Technical Field
The present disclosure relates to microelectronic devices that include three terminal devices having one or more layers of an amorphous metal film.
Description of the Related Art
Amorphous metals are rigid solid materials whose atomic structure lacks long-range periodicity that characterizes crystalline materials. In an amorphous metal, formation of crystalline planes is suppressed, for example, by incorporating two or more components. An example of an amorphous metal having four components—zirconium, copper, aluminum, and nickel—is Zr55Cu30Al10Ni5, as described in U.S. Pat. No. 8,436,337. Amorphous metals can be identified by their resistivity measurements, which have shown that an amorphous metal material, while still conductive, has about ten times greater resistivity than its crystalline counterpart. Amorphous metals also have smoother surfaces than crystalline metals, as indicated by root mean square (RMS) surface roughness measurements.
Amorphous multi-component metallic films (AMMFs), in the range of about 10-200 nm thick, can be used to improve the performance of electronic components such as resistors, diodes, and thin film transistors. Many deposition techniques that are well known in the art can be used to form AMMFs. For example, the exemplary amorphous metal noted above, Zr55Cu30Al10Ni5, is an AMMF and can be formed on a substrate by conventional sputter deposition using four different metal targets. It is understood by those skilled in the art of thin films that the interfacial properties of AMMFs are superior to those of crystalline metal films, and therefore electric fields at the interface of an AMMF and an oxide film are more uniform.
For example, such uniformity has produced superior current-voltage (I-V) characteristic curves for metal-insulator-metal (MIM) diodes and transistors that exhibit Fowler-Nordheim tunneling. The tunneling MIM diodes incorporate an AMMF as a lower electrode, and a crystalline metal film as an upper electrode. The two different electrodes are separated by a single dielectric barrier that provides a tunneling pathway for charge carriers to move between the electrodes. The presence of the single dielectric barrier results in a current response that depends on the polarity of the applied voltage. Such a current response can be referred to as one-way tunneling because at a specific voltage the charge carriers in the device are only tunneling in one direction. That is, tunneling occurs either from the lower electrode to the upper electrode, or from the upper electrode to the lower electrode, according to the polarity of the applied voltage. Various diode and transistor applications of AMMFs are discussed in U.S. Pat. Nos. 8,436,337 and 8,822,978.
Amorphous metal thin film non-linear resistors (AMNRs), having superior performance to existing thin film non-linear resistors, are discussed in U.S. Pat. No. 9,099,230 and PCT Patent Application No. WO2014/074360. Such AMNRs are of interest, in part, because their current response is independent of the polarity of the applied voltage, which is not true for other thin film resistors. This polarity independence is due to the presence of two dielectric barriers, wherein the charge carriers at each barrier are forced to tunnel in substantially opposite directions. AMNRs can be described as exhibiting two-way tunneling because, in response to an applied voltage, the charge carriers in the device tunnel in both directions across the barriers. That is, tunneling occurs from the upper electrode to the lower electrode and from the lower electrode to the upper electrode, regardless of the polarity of the applied voltage. Such polarity-symmetric AMNRs may provide improved signal control in liquid crystal display (LCD) or organic light emitting diode (OLED) display technologies and electromagnetic sensor arrays.